Effect of HIP post-processing at 850 °C/200 MPa in the fatigue behavior of Ti-6Al-4V alloy fabricated by Selective Laser Melting

Machine learning methods to predict the fatigue life of selectively laser melted Ti6Al4V components

“…Figure 5A shows the dataset “Gong 2015 SLM‐MP 4” 15 evaluated with the PINN algorithm; with respect to Figure 4B the quality has improved significantly as the behavior is smoother and strictly decreasing. The same holds for Figure 5B,C representing the datasets “DuQian2020, set 1” 5 and “Alegre2022 as built”, 9 respectively. Figure 5D depicts set “Li2016, Hooerweder et al” 19 Linear trends are also achieved by the PINN, as it is observable in Figure 5E,F showing the datasets “Gunther2017, SLM‐1 b” 6 and “Kumar2020 3067‐AF.” 13 According to Figure 5A,B,D–F, very good predictions can be obtained, with the predicted S‐N curves crossing the experimental data and, at the same time, being strictly decreasing, with a smooth trend and the concavity facing upward.…”

“…Figure 6A,B show the datasets “Gong2015 SLM‐MP 4” 15 and “DuQian2020, set 1,” 5 respectively. Figure 6C represents the set “Alegre2022 as built” 9 whose concavity is finally facing upward thanks to the bi‐linear trend enforcement. In Figure 6D, set “Li2016, Hooerweder et al” 19 is considered, while Figure 6E,F depict “Yan2019 AF” 14 and “Alegre2022 HIP” 9 sets, correspondingly.…”

“…However, these parameters are generally missing in literature papers, due to their small influences, and are not considered as input parameters for the developed NN, as this won't lead to obtain a fully populated TDB. Thermal treatments as annealing or HIP are also largely employed 9 and significantly affect the fatigue response. Since the powder is fused at high temperatures, with a rapid subsequent decrement, the final part can undergo distortions and residual stresses.…”

“…Post‐processing treatments can also affect the fatigue response. For example, to reduce the defect size, thermal treatments, such as hot isostatic pressing (HIP), are often employed 6,8–10 11 shot peening (SP), 12,13 polishing, surface mechanical attrition treatment (SMAT), 14 surface machining and sand blasting (SB) 15 can remove surface defects, improving the response to cyclic loads.…”

“…Similarly, surface treatments like laser shot peening (LSP), 11 shot peening (SP), 12,13 polishing, surface mechanical attrition treatment (SMAT), 14 surface machining and sand blasting (SB) 15 can remove surface defects, improving the response to cyclic loads. Due to these large number of factors, the design against fatigue loads of SLM Ti6Al4V parts can be rather difficult 5,6,8,9,11,15–22 . Methodologies allowing to consider the influence of the above‐described factors on the fatigue response would facilitate the design process, without compromising the part safety.…”